I just checked your account and I can see that you have created a Freelancer account. You need to have a Client account in order to post a job and hire a Freelancer for your Job.
You can be a Client and a Freelancer using the same account. You'll use the same account to log in to Upwork, but the two parts of your account will be kept entirely separate. You'll be able to easily switch between the two as needed. To create a Client account on your existing account, please follow up instructions in this help article.